Application Architectures

Application  Architectures

Applications are developed  to suport org in their business operations.Applications accept input,process the data based on business rules,and provide data as output. The functions performed by an application can be divided into three categories.They are

1.      User Services

2.      Business Services

3.      Data Services.

Each category is implemented as a layer in an application.
User Services :

            The user service layer constitutes the froent end of a solution.it is also called a presentation layer because it provides an interactive user interface.

Business Services :

            The business service layer controls the enforcement of business rules on the data of an org.

Data Services :

            The data service layer comprises the data and the functions for manipulating this data.

Types of  Application Architectures :

1. Single-tier Architecture
2. Two-tier Architecture
3. Three-tier Architecture
4. N-tier Architecture

Single-tier Architecture :

      In the case of single-tier architecture,a single executable file handles all functions relating to the user,business,and data services layers.Such an application is called a Monolithic application.Some of the very early COBOL programms performing extermely mission-critical opperations fall under this category.

 

Single-tier Architecture

Two-tier Architecture :

      The Two-tier architecture divides an application into following two components :

                  Client  : Implements the user interface.

                  Server : Stores Data.

 

Two-tier Architecture

In the case of two-tier architecture, the user and the data services are located separately,either on the same machine or on saperate machines.For Example  You might have an VB application ,Which provides the user interface and SQL Server 7.0 which manages data.

      In the two-tier archicturethe business service layer may be implemented in one of the following ways.

      By using FAT Client

      By Using FAT Sever

By Dividing the business services between the user services and the data services.

FAT Client :

                  In the case of fat clients the business service layer is combined with the user service layer.Clients execute the presentation logic and enforce business logic.The Server stores data and processes transactions.

     

FAT Sever :

                        In the two-tier archicture with a fat server, the business services layer is combined with the data services layer.As business services are  stored on theserver,most of the processing takes place on the server.

By Dividing the business services between the user services and the data services:

                  You can also implement a two-tier model in which the business services are distributed between the user sevices and data services.In this case the processing of business logic is distributed between the user and data services.

Three-tier Architecture :

                  In the case of three-tier architecture,all the three service layers reside separately,either on the same machine or on different machines.The user interface interacts with the business logic.The business logic validates the data sent by the interface and forwards it to the database if it conforms to the requirements. The froent-end only interacts with business logic,which inturn interacts with the database.

 

Three-tier Architecture

N-tier Architecture :

                  An n-tire application uses business objects for handling business rules and data access.It has multiple servers handling business services.This application architecture provides various advantages over other types of application architectures. Some of the advantage include extensibility,resilience to change,maintainability,and scalability of the application.